They have the same powers as a police constable to seize equipment and make arrests, but most people outside angling clubs are unaware of their existance.

But with the new coarse fishing season starting on Tuesday, the Environment Agency officers covering rivers across the North West hit the ground to raise their profile and crack down on licence evasion.

Nationally last year officers checked more than 70,000 licences and prosecuted more than 2,100 licence cheats. Between them, they were ordered to pay fines and costs in excess of £500,000.

In Lancashire and Cumbria last year more than 3,300 licences were checked and 135 people were prosecuted for fishing without a valid rod licence, up from 76 licence cheats in 2013.

Damien Linney, fisheries enforcement officer, said: “We want to get a peaceful resolution, it’s good for us and good for the angler.

“We go in at a low level and we’re open with them, but we are classified as constables.

“We ask for a person’s details and it’s an offence not to give them.

“If a person won’t tell us and is being difficult, we can seize their tackle. The idea is that they will want to come to our office and collect it, but if the equipment isn’t worth a lot, it doesn’t give us much bargaining power.

“The next step is arresting someone, but we always try to avoid that because it’s a lot of headaches for us.

“On the Ribble people are used to seeing us, but when you go to some fisheries and there are people who don’t know us, it can be more difficult.”

The Environment Agency’s work is intelligence-led, meaning that work is targeted in known illegal hotspots and in areas where there are reports of evasion.

One of the hotspots in Lancashire is a two-mile stretch along the River Ribble, starting at the Ticked Trout.

Damien added: “You go up to the north of the county and you might get one or two a year without a licence, but you might get 100 in a year in the Preston area. A lot of it’s about geography.

“By the Tickled Trout there’s a stretch two miles on the right hand side which is owned by Preston Council and is currently free of charge, though you still need a licence.

“The location is also very near a lot of estates, so every man and his dog comes down to catch the likes of chub, barbel, dace and eels. It’s the most prolific stretch on the river by far.”

Timing is also an important factor. The May bank holiday weekends are a particularly popular time for anglers across Cumbria and Lancashire and over the recent bank holiday weekends, Environment Agency teams have made 61 visits to waters across Cumbria and Lancashire, serving more than 62 report forms for illegal fishing and checking more than 628 anglers for rod licences.

When officers went on patrol along the Ribble in Preston on Tuesday, everyone they came across had a valid licence.

When questionning an angler, officers note down their serial numbers and location, as well as type of membership, so they can check trends and feed information back to other departments.

Currently there are around five per cent unlicenced anglers in the county, which is on a par with national figures. During 2014/2015, license cheats in Lancashire were order to pay fines and costs in excess of £18,800, and nationally, the Environment Agency received more than £21 million from rod licence sales.

Damien said: “The licence is a good income generator. We’re not grant funded from Central Government and the money is important for enforcement campaigns, regulation work and also goes towards habitat improvements.

“Officers also respond to incidents like pollution and provide support and advice for clubs.”

The maximum fine for fishing without a licence is £2,500 – whereas annual rod licences for trout and coarse fishing remain at £5 for 12 to 16 year olds, £18 for senior and disabled concessions and £27 for non-concessions. Children under 12 can fish for free.

Day tickets or membership to an angling club are also required for fishing.